1. Field of the Invention
The present invention relates to a structure having a three-dimensional network skeleton composed of a material including a noble metal, a method for producing the structure, a membrane electrode assembly for a fuel cell including the structure, and a fuel cell.
2. Description of the Related Art
A porous noble metal has widely been studied with the expectation that it can be applied to an electrode of a fuel cell.
A method for producing such a porous noble metal is described in Japanese Patent Laid-Open No. 2003-221601 (a U.S. equivalent is US2005/0079374A1).
Japanese Patent Laid-Open No. 2003-221601 describes a technique in which nanometer-sized silica particles are used as a template (adsorbent) in the production of a porous noble metal. Specifically, a noble metal compound is adsorbed onto an aggregate of the silica particles. After the noble metal compound is reduced into a noble metal, the silica particles are dissolved away with NaOH to produce a porous noble metal.
In the technique described in Japanese Patent Laid-Open No. 2003-221601, a porous noble metal is produced by a wet process. The present inventors accomplished the present invention through a study on a new method for producing a porous noble metal by a dry process.